Dengue Fever

What Is Dengue Fever?

Who Gets Dengue Fever and How?

What Are the Symptoms of Dengue Fever?

How Is Dengue Fever Diagnosed and Treated?

What Are the Complications of Dengue Fever?

How Is Dengue Fever Prevented?

Resources

Dengue (DENG-gay) fever is a serious illness commonly occurring in tropical and subtropical regions of the world. It is caused by a virus that passes from person to person through the bite of mosquitoes, and causes high fever and pain in the muscles, joints, and bones.

KEYWORDS

for searching the Internet and other reference sources

Aedes mosquito

Arbovirus

Flavivirus

Hemorrhagic fever

What Is Dengue Fever?

Dengue fever is characterized by a sudden high fever and severe pain in the muscles, joints, and bones. (It originally was named “break-bone fever.”) The disease is more likely to cause serious illness in children, and some cases are fatal. Dengue fever is caused by four varieties of flaviviruses*, which are part of the arbovirus* family of viruses. Each virus can cause illness, but being infected by one type does not make a person immune* to the other three.

*flaviviruses

(FLAY-vih-vy-ruh-sez) are a group of viruses that includes those that cause dengue fever and yellow fever.

*arbovirus

(ar-buh-VY-rus) is a member of a family of viruses that multiply in blood-sucking organisms, such as mosquitoes and ticks, and spread through their bites.

*immune

(ih-MYOON) means resistant to or not susceptible to a disease.

Who Gets Dengue Fever and How?

Dengue fever is widespread in Asia, Africa, South America, and Central America. About 20 million cases develop annually worldwide, and the number of cases is on the rise. It occurs most frequently in highly populated areas, often in cities. Although the number of places where dengue fever is found continues to grow, the disease remains rare in the United States, with most cases appearing in travelers arriving from other countries.

The virus does not spread directly from person to person. Instead, the bite of a mosquito, usually the female Aedes mosquito, transmits the disease. The insect takes in the virus with its meal of blood when it bites an infected person. Because the virus remains in the mosquito for the rest of its life, the mosquito can pass the infection to many people. In areas with large populations of mosquitoes, dengue fever epidemics* can occur.

*epidemics

(eh-pih-DEH-miks) are outbreaks of diseases, especially infectious diseases, in which the number of cases suddenly becomes far greater than usual. Usually, epidemics that involve worldwide outbreaks are called pandemics.

What Are the Symptoms of Dengue Fever?

A sudden high fever, sometimes reaching 104 or 105 degrees Fahrenheit, often is the first symptom. The affected person also may have a flushed (reddish) face. As other symptoms develop, a person might experience muscle, joint, or bone pain; a severe headache; a rash; pain behind the eyes; and signs of small hemorrhages*, such as bleeding gums,

*hemorrhages

(HEH-muh-rih-jes) are areas of uncontrolled or abnormal bleeding.

petechiae*, or a nosebleed. Fever typically lasts 2 to 7 days. Once the fever goes away, the other signs and symptoms usually fade as well. Some symptoms may linger for a few weeks.

*petechiae

(puh-TEE-kee-eye) are tiny dots of blood beneath the skin that indicate bleeding from small vessels.

This map shows the occurrence of Dengue fever and its relationship to the regions where the Aedes mosquito lives. The disease is widespread close to the equator, in the tropical areas of Asia, Africa, South America, and Central America, the mosquito’s preferred habitat.

How Is Dengue Fever Diagnosed and Treated?

Doctors typically diagnose dengue fever from a patient’s history of symptoms and risk factors, including whether that person has been anywhere where dengue fever is found. The doctor looks for three signs: high fever, pain, and rash. These symptoms are known as the dengue triad. To help confirm the diagnosis, doctors may order blood tests or tests on spinal fluid to look for antibodies* to the virus.

*antibodies

(AN-tih-bah-deez) are protein molecules produced by the body’s immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.

No specific treatment exists for dengue fever, but the disease usually clears up on its own. In serious cases, supportive care in a hospital can make recovery easier or even save a person’s life. It is important to drink plenty of fluids to avoid dehydration*. Over-the-counter medicine, such as acetaminophen (uh-see-teh-MIH-noh-fen), can relieve pain and fever while the disease runs its course.

*dehydration

(dee-hi-DRAY-shun) is a condition in which the body is depleted of water, usually caused by excessive and unre-placed loss of body fluids, such as through sweating, vomiting, or diarrhea.

What Are the Complications of Dengue Fever?

The most serious form of the disease is called dengue hemorrhagic (heh-muh-RAH-jik) fever, which is characterized by high fever, serious hemorrhage, pneumonia, and sometimes failure of the circulatory system* (heart failure) or shock*. People who develop dengue hemorrhagic fever usually require hospitalization, where they receive fluids. It is possible to die from this form of the disease, though most people recover.

*circulatory

(SIR-kyoo-luh-tor-e) system is the system composed of the heart and blood vessels that moves blood throughout the body.

*shock

is a serious condition in which blood pressure is very low and not enough blood flows to the body’s organs and tissues. Untreated, shock may result in death.

How Is Dengue Fever Prevented?

Scientists are working on a vaccine for dengue fever, but one is not yet available. The only way to control the spread of the disease is to reduce mosquito populations. Using pesticides, stocking lakes and ponds with special fish that eat mosquito larvae*, and covering or eliminating small pools of standing water in which the insects breed can help keep mosquito levels in check. People can protect themselves from bites by using insect repellent and wearing clothing that covers much of the body.

*larvae

(LAR-vee) are the immature forms of an insect or worm that hatches from an egg.

What’s in a Name?

The history of medicine is replete with fanciful names derived from the symptoms or causes of various medical conditions, like “break-bone fever.” Here are just a few:

• Alice in Wonderland syndrome a condition in which a person has delusions or hallucinations
• cri-du-chat, or cat-cry, syndrome a genetic disease with many symptoms, including mental retardation and a high-pitched, catlike mewing cry
• cauliflower ear thickening of the ear with distortion of the contours, also known as boxer’s ear
• happy puppet syndrome a genetic disorder marked by a jutting out of the jaw, seizures, and prolonged spasms of laughter
• jumping disease an exaggerated response to being startled, causing a person to jump, fling the arms around, and yell; sometimes called jumping Frenchmen of Maine disease after the French loggers it was first found to affect
• kissing disease infectious mononucleosis, an acute illness that can spread through saliva
• mitten hand a birth defect involving the fusion of several fingers, with a single fingernail
• vagabond’s disease discoloration of the skin in people who are exposed to lice bites over a long period of time.

See also

Ebola Virus Infection

Travel-related Infections

Yellow Fever

Resources

Organizations

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC offers information about dengue fever at its website.

Telephone 800-311-3435 http://www.cdc.gov

World Health Organization (WHO), Avenue Appia 20, 1211 Geneva 27, Switzerland. WHO posts fact sheets on dengue fever and information about outbreaks in different regions of the world on its website.

Telephone 011-41-22-791-2111 http://www.who.int

Dengue Fever

Definition

Dengue fever is a disease caused by one of a number of viruses that are carried by mosquitoes. These mosquitoes then transmit the virus to humans.

Description

The virus that causes dengue fever is called an arbovirus, which stands for arthropod-borne virus. Mosquitoes are a type of arthropod. In a number of regions, mosquitoes carry this virus and are responsible for passing it along to humans. These regions include the Middle East, the far East, Africa, and the Caribbean Islands. In these locations, the dengue fever arbovirus is endemic, meaning that the virus naturally and consistently lives in that location. The disease only shows up in the United States sporadically.

In order to understand how dengue fever is transmitted, several terms need to be defined. The word "host" means an animal (including a human) that can be infected with a particular disease. The word "vector" means an organism that can carry a particular disease-causing agent (like a virus or bacteria) without actually developing the disease. The vector can then pass the virus or bacteria on to a new host.

Many of the common illnesses in the United States (including the common cold, many viral causes of diarrhea, and influenza or "flu") are spread because the viruses that cause these illness can be passed directly from person to person. However, dengue fever cannot be passed directly from one infected person to another. Instead, the virus responsible for dengue fever requires an intermediate vector, a mosquito, that carries the virus from one host to another. The mosquito that carries the arbovirus responsible for dengue fever is the same type of mosquito that can transmit other diseases, including yellow fever. This mosquito is called Aedes egypti. The most common victims are children younger than 10 years of age.

Causes and symptoms

Dengue fever can occur when a mosquito carrying the arbovirus bites a human, passing the virus on to the new host. Once in the body, the virus travels to various glands where it multiplies. The virus can then enter the bloodstream. The presence of the virus within the blood vessels, especially those feeding the skin, causes changes to these blood vessels. The vessels swell and leak. The spleen and lymph nodes become enlarged, and patches of liver tissue die. A process called disseminated intravascular coagulation (DIC) occurs, where chemicals responsible for clotting are used up and lead to a risk of severe bleeding (hemorrhage).

After the virus has been transmitted to the human host, a period of incubation occurs. During this time (lasting about five to eight days) the virus multiplies. Symptoms of the disease appear suddenly and include high fever, chills, headache, eye pain, red eyes, enlarged lymph nodes, a red flush to the face, lower back pain, extreme weakness, and severe aches in the legs and joints.

This initial period of illness lasts about two or three days. After this time, the fever drops rapidly and the patient sweats heavily. After about a day of feeling relatively well, the patient's temperature increases again, although not as much as the first time. A rash of small red bumps begins on the arms and legs, spreading to the chest, abdomen, and back. It rarely affects the face. The palms of the hands and the soles of the feet become swollen and turn bright red. The characteristic combination of fever, rash, and headache are called the "dengue triad." Most people recover fully from dengue fever, although weakness and fatigue may last for several weeks. Once a person has been infected with dengue fever, his or her immune system keeps producing cells that prevent reinfection for about a year.

More severe illness may occur in some people. These people may be experiencing dengue fever for the first time. However, in some cases a person may have already had dengue fever at one time, recovered, and then is reinfected with the virus. In these cases, the first infection teaches the immune system to recognize the presence of the arbovirus. When the immune cells encounter the virus during later infections, the immune system over-reacts. These types of illnesses, called dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS), involve more severe symptoms. Fever and headache are the first symptoms, but the other initial symptoms of dengue fever are absent. The patient develops a cough, followed by the appearance of small purplish spots (petechiae) on the skin. These petechiae are areas where blood is leaking out of the vessels. Large bruised areas appear as the bleeding worsens and abdominal pain may be severe. The patient may begin to vomit a substance that looks like coffee grounds. This is actually a sign of bleeding into the stomach. As the blood vessels become more damaged, they leak more and continue to increase in diameter (dilate), causing a decrease in blood flow to all tissues of the body. This state of low blood flow is called shock. Shock can result in damage to the body's organs (especially the heart and kidneys) because low blood flow deprives them of oxygen.

Diagnosis

Diagnosis should be suspected in endemic areas whenever a high fever goes on for two to seven days, especially if accompanied by a bleeding tendency. Symptoms of shock should suggest the progression of the disease to DSS.

The arbovirus causing dengue fever is one of the few types of arbovirus that can be isolated from the serum of the blood. The serum is the fluid in which blood cells are suspended. Serum can be tested because the phase in which the virus travels throughout the bloodstream is longer in dengue fever than in other arboviral infections. A number of tests are used to look for reactions between the patient's serum and laboratory-produced antibodies. Antibodies are special cells that recognize the markers (or antigens) present on invading organisms. During these tests, antibodies are added to a sample of the patient's serum. Healthcare workers then look for reactions that would only occur if viral antigens were present in that serum.

Treatment

There is no treatment available to shorten the course of dengue fever, DHF, or DSS. Medications can be given to lower the fever and to decrease the pain of muscle aches and headaches. Fluids are given through a needle in a vein to prevent dehydration. Blood transfusions may be necessary if severe hemorrhaging occurs. Oxygen should be administered to patients in shock.

Prognosis

The prognosis for uncomplicated dengue fever is very good, and almost 100% of patients fully recover. However, as many as 6-30% of all patients die when DHF occurs. The death rate is especially high among the youngest patients (under one year old). In places where excellent medical care is available, very close monitoring and immediate treatment of complications lowers the death rate among DHF and DSS patients to about 1%.

Prevention

Prevention of dengue fever means decreasing the mosquito population. Any sources of standing water (buckets, vases, etc.) where the mosquitoes can breed must be eliminated. Mosquito repellant is recommended for those areas where dengue fever is endemic. To help break the cycle of transmission, sick patients should be placed in bed nets so that mosquitoes cannot bite them and become arboviral vectors.

Resources

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. 〈http://www.cdc.gov〉.

KEY TERMS

Endemic— Naturally and consistently present in a certain geographical region.

Host— The organism (such as a monkey or human) in which another organism (such as a virus or bacteria) is living.

Vector— A carrier organism (such as a fly or mosquito) that delivers a virus (or other agent of infection) to a host.

Dengue Fever

Resources

Dengue fever is an illness caused by four closely related viruses (DEN-1, DEN-2, DEN-3, and DEN-4). Even though these viruses are closely related, they are recognized by the immune system as being different from each other. Thus, an infection with one virus does not provide immune protection against infections with the remaining three viral types. A person can have four bouts of dengue fever in his/her lifetime. With repeated infections of dengue fever, a person’s chances of developing the hemorrhagic form of the disease increase. Dengue hemorrhagic fever (DHF) occurs when a person who has immunity to one or more types of dengue virus is infected with another type of dengue virus. DHF causes bleeding and shock, and carries a higher mortality rate than standard dengue fever.

Dengue fever is a tropical disease. This is because the virus is carried mainly by a mosquito called Aedes aegypti. This mosquito is a normal resident of tropical and subtropical climates and feeds during the daytime. When an infected mosquito bites a human to obtain its blood meal, the virus can be transmitted to humans.

The reverse is true as well; the virus can be sucked up into a mosquito if the mosquito feeds on a dengue-infected human. The virus can subsequently be spread to another person. In this way, a large number of dengue fever cases can appear in a short time. Furthermore, if more than one of the dengue viruses is in circulation at the same time, more than one dengue fever epidemic can occur simultaneously.

Like mosquitoes, the dengue viruses have been around for centuries. The first written records of dengue fever epidemics date back to the late eighteenth century. The last major global epidemic began just after World War II. This epidemic is ongoing and has grown worse since 1990, especially in South and Central America, Caribbean nations, and in Asia. Currently, the World Health Organization estimates that over two billion people are exposed to dengue fever, and more than 100 million people, mostly children, contract the disease annually.

Dengue, also called breakbone or dandy fever (because of the severe joint and muscle pain that can result from the infection), is endemic to the tropics, meaning that the virus is always present in the environment. The dengue viruses belong to the arbovirus group. The term arbovirus is a derivative for arthropod borne, reflecting the fact that the viruses are transmitted by an insect.

The incubation period for dengue fever is usually five to eight days, but may be as few as three or as many as 15 days. Once the virus has had a sufficient incubation, the onset of the disease is sudden and dramatic. The first symptom is usually sudden chills. A headache follows and the person with dengue feels pain with eye movement. Within hours the person is often debilitated by extreme pain in the legs and joints. Body temperature may rise to 104°F (40°C). A pale rash may appear, usually on the face, but it is transient and soon disappears.

These symptoms persist for up to 96 hours, followed by a rapid loss of fever and profuse sweating. The patient begins to feel better for about a day, and then a second bout of fever occurs. This temperature rise is rapid, but peaks at a lower level than the first episode. A rash appears on the extremities and spreads rapidly to the trunk and face. Palms of the hands and soles of the feet may become bright red and swollen.

There is no cure for dengue. Treatment is palliative, that is, intended to ease the symptoms of the disease. Individuals usually recover completely from dengue after a convalescent period of several weeks with general weakness and lack of energy. If dengue hemorrhagic fever develops, roughly half of all persons who develop shock will survive.

No vaccine is available to prevent the disease, however, a trials for a new dengue vaccine for children are set to begin in 2007. In the meantime, the territory of the Aedes mosquito is expanding, and the only preventive measure that can be taken is to eradicate the mosquito or to reduce exposure to them. Full-coverage clothing, mosquito netting, mosquito repellent containing DEET can all help to protect individuals. Persons who have the disease should be kept under mosquito netting to prevent mosquito bites, which can then spread the virus.

See also Insecticides.

Resources

BOOKS

White, Katherine. Dengue Fever (Epidemics) New York: Rosen, 2003.

PERIODICALS

Walsh, Nancy. “Dengue Fever: A Souvenir of Tropical Trips” Skin and Allergy News 35 (July 1, 2004): 55.

OTHER

Centers for Disease Control and Prevention. “Dengue Fever.” <http://www.cdc.gov/ncidod/dvbid/dengue/> (accessed March 7, 2007).

Brian Hoyle

Dengue fever

Dengue fever is a debilitating and sometimes hemorrhagic fever (one that is associated with extensive internal bleeding). The disease is caused by four slightly different types of a virus from the genus Flavivirus that is designated as DEN. The four antigenic types are DEN-1, DEN-2, DEN-3, and DEN-4.

The dengue virus is transmitted to humans via the bite of a mosquito. The principle mosquito species is known as Aedes aegypti. This mosquito is found all over the world, and, throughout time, became adapted to urban environments. For example, the mosquito evolved so as to be capable of living year round in moist storage containers, rather than relying on the seasonal patterns of rainfall. Another species, Aedes albopictus (the "Tiger mosquito"), is widespread throughout Asia. Both mosquitoes are now well established in urban centers. Accordingly, dengue fever is now a disease of urbanized, developed areas, rather than rural, unpopulated regions.

The dengue virus is passed to humans exclusively by the bite of mosquito in search of a blood meal. This mode of transmission makes the dengue virus an arbovirus (that is, one that is transmitted by an arthropod). Studies have demonstrated that some species of monkey can harbor the virus. Thus, monkeys may serve as a reservoir of the virus. Mosquitoes who bite the monkey may acquire the virus and subsequently transfer the virus to humans.

The disease has been known for centuries. The first reported cases were in 1779–1780, occurring almost simultaneously in Asia, Africa, and North America. Since then, periodic outbreaks of the disease have occurred in all areas of the world where the mosquito resides. In particular, an outbreak that began in Asia after World War II, spread around the world, and has continued to plague southeast Asia even into 2002. As of 2001, dengue fever was the leading cause of hospitalization and death among children in southeast Asia.

Beginning in the 1980s, dengue fever began to increase in the Far East and Africa. Outbreaks were not related to economic conditions. For example, Singapore had an outbreak of dengue fever from 1990 to 1994, even after a mosquito control program that had kept the disease at minimal levels for over two decades. The example of Singapore illustrates the importance of an ongoing program of mosquito population control.

The disease is a serious problem in more than 100 countries in Africa, North and South America, the Eastern Mediterranean, South-East Asia, and the Western Pacific.

Unlike other bacterial or viral diseases, which can be controlled by vaccination , the four antigenic types of the dengue virus do not confer cross-protection. Thus, it is possible for an individual to be sickened with four separate bouts of dengue fever.

Following the transfer of the virus from mosquito to humans, the symptoms can be varied, ranging from nonspecific and relatively inconsequential ailments to severe and fatal hemorrhaging. The incubation period of the virus is typically 5 to 8 days, but symptoms may develop after as few as three days or as many as 15 days. The onset of symptoms is sudden and dramatic. Initially, chills tend to develop, followed by a headache. Pain with the movement of the eyes leads to more generalized and extreme pain in the legs and joints. A high fever can be produced, with temperatures reaching 104° F [40° C]. Also, a pale rash may appear transiently on the face.

These symptoms can persist for up to 96 hours. Often, the fever then rapidly eases. After a short period when symptoms disappear, the fever reappears. The temperature elevates rapidly but the fever is usually not as high as in previous episodes. The palms of the hands and soles of the feet may turn bright red and become very swollen.

In about 80% of those who are infected, recovery is complete after a convalescent period of several weeks with general weakness and lack of energy. However, in some 20% of those who are infected a severe form of dengue fever develops. This malady is characterized by the increased leakage of fluid from cells and by the abnormal clotting of the blood. These factors produce the hemorrhaging that can be a hallmark of the disease, which is called dengue hemorrhagic fever. Even then, recovery can be complete within a week. Finally, in some of those who are infected, a condition called dengue shock syndrome can result in convulsions. In addition, a failure of the circulatory system can occur, resulting in death.

The reasons for the varied degrees of severity and symptoms that the viral infection can elicit are still unclear. Not surprisingly, there is currently no cure for dengue, nor is there a vaccine . Treatment for those who are afflicted is palliative, that is, intended to ease the symptoms of the disease. Upon recovery, immunity to the particular antigenic type of the virus is in place for life. However, an infection with one antigenic type of dengue virus is not protective against the other three antigenic types. Currently, the only preventive measure that can be taken is to eradicate the mosquito vector of the virus.

See also Epidemics, viral; Zoonoses

Dengue fever

Dengue fever is an illness caused by four closely related viruses (DEN-1, DEN-2, DEN-3, and DEN-4). Even though these viruses are closely related, they are recognized by the immune system as being different from each other. Thus, an infection with one virus does not provide immune protection against infections with the remaining three viral types. A person can have four bouts of dengue fever in his/her lifetime.

Dengue fever is a tropical disease . This is mainly because the virus is carried by a mosquito called Aedes aegypti. This mosquito is a normal resident of tropical climates. When the mosquito bites a human to obtain its blood meal, the virus can be transmitted to humans.

The reverse is true as well; the virus can be sucked up into a mosquito if the mosquito feeds on a dengue-infected human. The virus can subsequently be spread to another person. In this way, a large number of dengue fever cases can appear in a short time. Furthermore, if more than one of the dengue viruses is in circulation at the same time, more than one dengue fever epidemic can occur simultaneously.

Like mosquitoes , the dengue viruses have been around for centuries. The first written records of dengue fever epidemics date back to the late eighteenth century. The last major global epidemic began just after World War II. This epidemic is ongoing and has grown worse since 1990.

Dengue, also called breakbone or dandy fever (because of the severe joint and muscle pain that can result from the infection), is endemic to the tropics, meaning that the infection is always present. The dengue viruses belong to the arbovirus group. The term arbovirus is a derivative for arthropod borne, reflecting the fact that the viruses are transmitted by an insect.

The incubation period for dengue fever is usually five to eight days, but may be as few as three or as many as 15 days. Once the virus has had a sufficient incubation, the onset of the disease is sudden and dramatic. The first symptom is usually sudden chills. A headache follows and the patient feels pain with eye movement. Within hours the patient is debilitated by extreme pain in the legs and joints. Body temperature may rise to 104°F (40°C). A pale rash may appear, usually on the face, but it is transient and soon disappears.

These symptoms persist for up to 96 hours, followed by a rapid loss of fever and profuse sweating. The patient begins to feel better for about a day, and then a second bout of fever occurs. This temperature rise is rapid, but peaks at a lower level than the first episode. A rash appears on the extremities and spreads rapidly to the trunk and face. Palms of the hands and soles of the feet may turn bright red and swollen.

There is no cure for dengue. Treatment is palliative, that is, intended to ease the symptoms of the disease. Individuals usually recover completely from dengue after a convalescent period of several weeks with general weakness and lack of energy .

Recently, attenuated forms of all four dengue viruses have been developed in Thailand. These weakened viruses may be candidates for use in vaccines, even a vaccine that would simultaneously protect someone from all four versions of dengue fever. However, such a vaccine is still years from production.

No vaccine currently exists to prevent the disease. The only preventive measure that can be taken is to eradicate the aedes mosquito or to reduce exposure to them. Patients who have the disease should be kept under mosquito netting to prevent mosquito bites, which can then spread the virus.

See also Insecticides.

Resources

books

gubler, d. j., g. kuno, and k. gubler. dengue and denguehemorrhagic fever. new york: cabi publishing, 1997.

richman, d. d., r. j. whitley, and f. g. hayden. clinical virology. 3rd ed. washington, dc: american society for microbiology press, 2002.

periodicals

kuhn, r. j., et al. "structure of dengue virus: implications for flavivirus organization, maturation, and fusion." cell 108 (march 2002): 717–725.

other

centers for disease control and prevention. division of vector-borne infectious diseases. po box 2087, fort collins, co 80522. <http://www.cdc.gov/ncidod/dvbid/dengue//>.

Brian Hoyle